Regras de inflexão rails

https://books.google.com.br/books?id=OoPkpcMpGnkC&pg=PA407&lpg=PA407&dq=Regras+de+inflex%C3%A3o+rails&source=bl&ots=2I_r5nuhBy&sig=ACfU3U0FT54etBXR7iD5cbWKH3xBm-Muzw&hl=pt-BR&sa=X&ved=2ahUKEwj5tN6r_a_lAhXmwVkKHWCjAToQ6AEwA3oECAkQAQ#v=onepage&q=Regras%20de%20inflex%C3%A3o%20rails&f=false